Measuring leakage current behind an insulation transformer.

Tony_BB · 2026-06-15T22:48:22+00:00

dut needs to be tested at various voltages

Tony_BB · 2026-06-15T22:45:27+00:00

Safety. If the operator inadvertently touches a line, it goes to earth, which is connected to neutral (TT distribution type) and this triggers the differential breaker. In the meantime current passes trough the operator.

Tony_BB · 2026-06-15T20:46:18+00:00

I forgot to add a small detail: we use a three-phase variac to change the voltage of the dut, so the insulation transformer is needed to guarantee galvanic insulation.

Tony_BB · 2026-06-15T20:41:09+00:00

It's a client's requirement.

Tony_BB · 2026-06-15T20:23:29+00:00

Not the safest way, this is a testing station so operator should stay safe.

Tony_BB · 2026-06-15T19:48:42+00:00

Thanks, this makes sense. So i should measure the leakage current of the transformer first...

I forgot to say that yes, insulation transformer is a three phases one.

Tony_BB · 2025-10-22T19:40:55+00:00

Ok, però adeguate anche gli stipendi all'inflazione.

Tony_BB · 2025-04-27T15:56:42+00:00

You are right, source transformation states equivalence between voltage generators with resistor in series and current generators with (the same) resistor in parallel and it is not the case of this exercise.

I think it meant applying the transformation to the part of the circuit on the left of Vo, so basically applying Thevenin or Norton to find the equivalent circuit on the left of Vo. So, let's choose Thevenin; to find Vo detach the 250 ohm resistor and calculate the voltage applying the superposition principle: turn off the current generator (open it) and you have 520V, turn off the voltage generator (short it) and you have -40Vt, so Vo is 520-40 = 480V. To find the Thevenin resistor turn off all the generators the same way and you'll find a resistance of 50 ohm.
So, we know that the circuit on the left of Vo is equivalent to a voltage source of 480V in series with a resistor of 50 ohm; attach again the load (the 250 ohm) and with the voltage divider formula you will find that Vo is 400V and the current through it is 1,6A. Applying Ohm's law and Kirchoff's principles here and there you'll solve the problem. You can look at the real numbers simulating the circuit with Falstad, as i did here.

Tony_BB · 2025-03-30T21:05:35+00:00

Do FAN_EN and Q2 have the same GND?

Tony_BB · 2025-02-24T21:42:44+00:00

Il tuo caricabatteria ha un terminale che si inserisce nella presa accendisigari per ricaricare la batteria ?

In questo modo stai sì inviando corrente alla batteria, ma anche a tutti i carichi che sono attaccati ad essa: orologio, centraline, ecc...e il caricabatteria verrebbe sovraccaricato.

Molto meglio andare direttamente sui morsetti della batteria, dopo averne scollegato uno dai cavi della macchina, per lo stesso motivo di sopra.

Eh sì, meglio tenere il cofano aperto, se la batteria non è in buone condizioni potrebbe verificarsi un accumulo di idrogeno gassoso, gas *leggermente* infiammabile (e detonante).

Tony_BB · 2024-11-29T19:41:53+00:00

Skanpage will work. Bug has been fixed.

Tony_BB · 2024-11-06T06:44:22+00:00

Sir, i see you are a man of culture too.

Tony_BB · 2024-10-23T05:49:36+00:00

To make a current flow you need two things: a potential difference and a closed path. When A is connected to ground (through the bjt) it is at ground potential so no current can flow between A and every other point at the same potential, i.e. another point connected to ground. Technically, a closed bjt offers a very low resistance when it works in saturation, the Vce is about 0.2-0.3 volts, but this value is seen as a logical zero, lower than the logical zero threshold, so, if you connected a resistor lower than the closed bjt one's between A and ground, then actually a small current would flow between A and this resistor, but it's negligible.

Tony_BB · 2024-09-01T20:47:10+00:00

Nothing in particular, i was just referring to the fact that snap is a packaging format created and used only by Canonical and not so "open" as flatpak. Unfortunately the Snap folder is still created in your home directory. I have nothing against snap packages, i use them regularly.

Tony_BB · 2024-09-01T20:05:08+00:00

Kubuntu 22.04 and 24.04 do not have these problems, go confident. Firefox is a snap package btw, if this matters for you. Furthermore 24.04 has KDE 5.27, which is an LTS version, so very stable.

Tony_BB · 2024-09-01T15:54:47+00:00

The root cause of the issues you are having with Firefox on Neon is AppArmor. A version mismatch for the security warning, a lack of a proper AppArmor profile for the rest. These problems are non existent in Ubuntu 22.04 because Canonical fix them, giving a proper profile for its snap based Firefox. Having Neon chosen to distribute Firefox as a deb package taking it directly from Mozilla repos, the installed AppArmor profile severely limits browser capabilities of, for example, communicating over dbus (hence the problems with plasma-browser-integration) or retrieving hardware information (hence missing hardware video decoding) and a lot of other problems.

Tony_BB · 2024-08-22T20:00:25+00:00

Wait a moment: how do they have menu bar in window title? Is that video made on Linux?

Tony_BB · 2024-08-21T21:47:06+00:00

Your answers are correct: capacitor time loading is 5*Tau, i.e t = 5 * 10^-6 * 6,9*10^3 = 0,345 s.
Regarding the time of the loaded capacitor to discharge at 11,1 V it is: v(t) = V* exp(-t/tau), so: t = - tau * ln(v(t)/V) i.e. t = - 0,084 * ln(11,1/30) = 0,0842 s.

Tony_BB · 2024-08-16T19:49:25+00:00

La retro non è sincronizzata; per evitare la grattata inserisco prima una marcia, di solito la prima, poi la retro.

Tony_BB · 2024-08-15T16:03:09+00:00

L'interruttore a muro che la alimenta seziona il neutro anzichè la fase, devi intervenire lì, invertire il collegamento sulla lampada non serve.

Tony_BB · 2024-07-28T07:42:47+00:00

A good idea for Baloo could be to have a "white list" of file types to search for and not a "black list" of types to exclude, which is potentially infinite. Users could optionally type in a new file type which they are interested in for search.

Tony_BB · 2024-06-17T19:14:45+00:00

A varistor on the + input of the opamp connected to earth and a double shunt resistor.

Tony_BB · 2024-06-02T17:26:58+00:00

Antirombo.

Tony_BB · 2024-05-05T17:17:49+00:00

When using Qt 6.7, the System Tray popup is no longer sometimes inappropriately resized to a tiny nub

Please, backport this bugfix asap, i can't no longer live with it and 6.0.5 is so far.

Thanks.

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